Re: Problem for Bittorrent Application behind Linux Firewall

[Harald Welte <laforge@netfilter.org>]

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On Tue, Sep 23, 2003 at 05:16:41PM +0800, Tom wrote:
> The following is my iptables rules.According to my understanding, BT
> use the ports 6881 to 6889,Then I forward these ports to my machines
> in LAN.

I have no idea about bittorrent and it's protocol, sorry.
> 
> #! /bin/sh
> iptables -t nat -A PREROUTING -i ppp0 -p tcp --dport 6881:6889 -j DNAT --to 192.168.1.90:6881-6889
> iptables -A FORWARD -p tcp -s 192.168.1.90 --dport 6881:6889 -j ACCEPT
> 

Those rules say 'nat any port between 6881:6889 to any port between
6881:6889'.  i.e. port 6881 can be NAT'ed to 6884, happening in a
non-deterministic manner.

try 9 seperate rules for every port if you want to have that guarantee.
 
> Tom Cheung
> 23 Sept 2003
-- 
- Harald Welte <laforge@netfilter.org>             http://www.netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie

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